Clinical and haemodynamic effects of diazoxide in primary pulmonary hypertension.

Diazoxide was injected into the pulmonary artery in nine patients with primary pulmonary hypertension. There was no significant change in pulmonary artery pressure, which fell by more than 10 mmHg in only two patients. The pulmonary blood flow increased in all patients as a result of a fall in pulmonary vascular resistance (by 4 to 17 units). Systematic vasuclar resistance also fell as expected in all patients. Oral diazoxide was given to seven patients, two of whom showed sustained clinical improvement while remaining on treatment (400 to 600 mg daily). Five patients were unable to tolerate the drug, because of nausea and sickness (two), peripheral oedema requiring large doses of diuretics (four), diabetes (three), and postural hypotension (one). Hirsutes was troublesome in the two patients remaining on treatment. Diazoxide may be useful in the management of some patients with primary pulmonary hypertension, but its use is limited by the frequency of side effects. Our results suggest that examination of othe potent vasodilators may be worth while.